1. Field of the Invention
The present invention relates to a digital display apparatus, and more particularly to a flat display apparatus capable of adjusting the vertical size of the display image.
2. Description of the Related Art
In analog display apparatus using Cathode Ray Tubes (CRTs), the adjustment of the horizontal size and vertical size of the display image has been performed by the deflection control that controls the amount of currents flowing through the horizontal and vertical deflection yokes provided around the neck of the CRT.
However, as for so-called flat panel display apparatus driven by digital video signals, such as plasma displays (PDPs), liquid crystal displays (LCDs), and so on, the display image size adjustment through the conventional method is impossible. Thus, in order to adjust the size of the image in a digital display apparatus, it is necessary to process the digital video signals through a digital data conversion.
The patents to Takeuchi, U.S. Pat. Nos. 5,422,678 and 5,555,027, respectively entitled Video Processor For Enlarging And Contracting An Image In A Vertical Direction and VIDEO PROCESSOR FOR ENLARGING AND CONTRACTING AN IMAGE IN A VERTICAL DIRECTION, disclose a video processor which is capable of arbitrarily expanding or contracting an image in a vertical direction. However, the system of Takeuchi requires programmable frequency dividers as well as a video memory in order to effect the adjustment of the size in a vertical direction.
The following patents each disclose features in common with the present invention but are not as pertinent as the Takeuchi patents noted above: U.S. Pat. No. 5,262,720 to Senn et al., entitled Circuit For Controlling The Lines Of A Display Screen And Including Test Means With A Single Output, U.S. Pat. No. 5,528,268 to Ni et al., entitled Control Method And Device For A Monitor, U.S. Pat. No. 5,027,036 to Ikarashi et al., entitled Drive Circuit For An Electroluminescence Display Device, U.S. Pat. No. 5,532,716 to Sano, entitled Resolution Conversion System, U.S. Pat. No. 5,555,002 to Nguyen, entitled Method And Display Control System For Panning, U.S. Pat. No. 5,576,732 to Minakuchi et al., entitled Dynamic Image Display Device, U.S. Pat. No. 5,406,308 to Shiki, entitled Apparatus For Driving Liquid Crystal Display Panel For Different Size Images, U.S. Pat. No. 4,916,747 to Arimoto, entitled Image Processing System, and U.S. Pat. No. 4,952,923 to Tamura, entitled Display Apparatus With Image Expanding Capability.